The solar system revolves around the star b.
Star b orbits star c.
Star c revolves around star d.
And ....
They all revolve around the center of the Milky Way.
Why b star (Grand mother) has not been discovered yet, when we can easily see it.
Some reasons for not identifying the star b:
1- The earth revolves around the sun at a much faster speed. The earth also rotates around itself. And it makes it difficult to detect the star b from the surface of the earth. If we are on the surface of the sun, we can easily recognize the star b.
2- Maybe:
The rotation of our sun around b occurs in a very elongated ellipse. As a result, we think we are moving closer or further away from star b. And we do not notice the rotation of the sun.
3- Maybe:
Most likely, the Sun revolves around star b from east to west.
Like the planet Pluto.
4- In a very long time, the solar system revolves around star b. And we need enough time to detect star b.
I have some solutions that will help you find the granny star quickly. I will present soon.
In my opinion, our second sun: (grandmother) is the night star.
The Sun is not part of a multiple-star system, so it does not revolve around ANY other star. It DOES revolve around the center of the galaxy, and passes other stars (or vice-versa) many, many times during a given orbit (which takes about 100 million years), but it just PASSES them. It does NOT join any of them and become part of a multiple-star system. So there is no Grandma Star for our Sun. (There ARE multiple-star systems, but even in those, unless one happens to be much more massive than the others, they all move around the others as siblings, not parents and children.)